WO2021168600A1

WO2021168600A1 - Prussian blue sodium ion battery positive electrode material having low moisture content, preparation method therefor, and sodium ion battery

Info

Publication number: WO2021168600A1
Application number: PCT/CN2020/076348
Authority: WO
Inventors: 侴术雷; 王晚林; 李用成; 李东祥; 宫毅涛; 李亚书
Original assignee: 辽宁星空钠电电池有限公司
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2021-09-02
Also published as: CN115023829A

Abstract

Disclosed are a Prussian blue sodium ion battery positive electrode material having low moisture content, a preparation method therefor, and a sodium ion battery. The method comprises the following steps: (1) dissolving a transition metal salt, an antioxidant, a complexing agent, a pH regulator, and a sodium salt into water to obtain a mixed solution containing the transition metal salt; (2) dissolving sodium ferrocyanide, the pH regulator, and the sodium salt into water to obtain a mixed solution containing the sodium ferrocyanide; (3) dropwise adding the mixed solution containing the transition metal salt and the mixed solution containing the sodium ferrocyanide to a container, then performing stirring, standing, and then performing washing, filtering or centrifugation, and spray drying to obtain the Prussian blue sodium ion battery positive electrode material; and (4) performing thermal treatment at an inert atmosphere or vacuum drying on the battery positive electrode material. The battery positive electrode material of the present invention is high in sodium content, low in moisture content, and excellent in electrochemical performance. The method of the present invention is simple in production process, high in production efficiency, cheap in used raw materials, and easy to achieve large-scale production.

Description

Prussian blue sodium ion battery cathode material with low moisture content, preparation method thereof and sodium ion battery

Technical field

The invention belongs to the technical field of new energy storage materials, and specifically relates to a Prussian blue cathode material with low moisture content and a preparation method thereof, and a sodium ion battery.

Background technique

Due to people’s long-term over-reliance on and use of fossil energy, global greenhouse effect and environmental pollution problems are increasing, the development and utilization of renewable clean energy has become urgent. Clean energy such as wind, solar, tidal energy, etc. can be achieved through battery energy storage devices. Effectively realize energy storage and utilization. In 1990, Japan's SONY company realized the industrialization of lithium-ion batteries for the first time. Until today, the battery market is dominated by lightweight, high-energy-density lithium-ion batteries. However, lithium resources are limited and the price continues to rise. In contrast, sodium is widely distributed, rich in resources, and low in price. Therefore, the development and utilization of sodium-ion batteries has become an effective means to replace lithium-ion batteries in the future. Due to the similar chemical properties of sodium and lithium, sodium ion batteries are expected to become the most potential battery energy storage device in the future.

The important components of sodium ion battery mainly include positive electrode, negative electrode material, electrolyte, separator and so on. Among them, the research on positive and negative materials is particularly prominent. For example, the negative electrode material is mainly based on relatively stable hard carbon, which has been mass-produced in Japan. The composition of the sodium-ion battery electrolyte is very similar to that of the lithium-ion electrolyte, and is mainly an organic ester electrolyte containing sodium salt and functional additives. However, due to the large radius of sodium ions, the structural instability of the cathode material during charge and discharge has become a key factor restricting the development of sodium ion batteries. Among different types of cathode materials for sodium ion batteries, Prussian blue-based cathode materials have a simpler phase transition process than layered oxides and polyanionic materials, and the frame structure of Prussian blue is conducive to sodium ions. Rapid deintercalation, so the structure is relatively stable during charging and discharging. In recent years, it has attracted the attention of a large number of researchers. Another significant advantage of Prussian blue materials is that the synthesis process is simple and does not require high temperature compared with traditional cathode materials. Sintering can greatly reduce the cost of material production.

Prussian blue-based sodium ion battery cathode materials can be synthesized by thermal decomposition, hydrothermal, and co-precipitation methods. Among them, the thermal decomposition method and the hydrothermal method both adopt the single iron source decomposition principle of sodium ferrocyanide, and the obtained product has fewer lattice defects and lower water content, but the production efficiency and yield of these two methods are low, and the synthesis process The toxic by-products of NaCN produced in it pollute the environment and are not conducive to large-scale production. However, the co-precipitation method is a green and environmentally friendly method that can achieve expanded production. The method of preparing Prussian blue cathode material by the co-precipitation method currently reported in the patent literature mainly includes: a method of preparing Prussian blue cathode material and sodium ion battery (CN107364875A), a preparation method and application of low-defect nano-Prussian blue (CN106745068A), etc. However, the above synthesis method simply mixes the transition metal salt and sodium ferrocyanide solution, and the reaction speed is difficult to control, resulting in poor crystallinity of the material, low sodium content, high moisture content in the material, and relatively high electrochemical performance. Poor, which in turn affects practical applications.

The moisture content in the Prussian blue cathode material of sodium ion battery plays a vital role in its electrochemical performance. The moisture in Prussian blue is caused by defects in the synthesis process. Too high moisture content will lead to a decrease in the specific capacity of the material. Water and electrolysis The side reaction of the liquid will also cause the reduction of rate performance and cycle performance. How to effectively reduce the moisture content of Prussian blue materials, first of all, the key is to control the sodium ion concentration in the solution during the co-precipitation reaction and the reaction speed of transition metal ions with ferrocyanide. A slow co-precipitation rate can obtain a higher sodium content and a higher moisture content. Less Prussian blue cathode material. In addition, further dehydration treatment of the Prussian blue cathode material can further reduce the moisture content and improve the electrochemical performance. Therefore, how to prepare Prussian blue-type sodium ion battery cathode materials with low moisture content has become a direction of future research and development.

Summary of the invention

The purpose of the present invention is to provide a Prussian blue cathode material with low moisture content and a preparation method thereof. The method is simple and easy to implement, has high production efficiency, the prepared material has very low moisture content or no moisture, and the material has excellent electrochemical performance.

In order to achieve the above-mentioned objective, the first aspect of the present invention provides a method for preparing a Prussian blue sodium ion battery cathode material with a low moisture content. The preparation method includes the following steps:

(1) Dissolve transition metal salts, antioxidants, complexing agents, pH regulators, and sodium salts in water under an inert atmosphere and a certain temperature to obtain a mixed solution containing transition metal salts;

(2) Dissolve sodium ferrocyanide, pH adjuster, and sodium salt in water under an inert atmosphere and a certain temperature to obtain a mixed solution containing sodium ferrocyanide;

(3) Add dropwise the mixed solution containing transition metal salt and the mixed solution containing sodium ferrocyanide into a container with an inert atmosphere and a certain temperature, and then stir, stand still, and then wash, filter or centrifuge , Spray drying to obtain powdered Prussian blue sodium ion battery cathode material;

(4) The powdered Prussian blue sodium ion battery cathode material is subjected to inert atmosphere heat treatment or vacuum drying to obtain a Prussian blue sodium ion battery cathode material with low moisture content.

According to the present invention, preferably, the molecular formula of the Prussian blue sodium ion battery cathode material with low moisture content is Na _x M _a N _b Fe(CN) ₆ ·yH ₂ O, where 1.8<x<2, 0≤y≤3 ; M and N are transition metals, each independently selected from at least one of Fe, Co, Mn, Ni, Cu, Zn, Cr, V, Zr and Ti, where 0<a<1, 0<b<1 , A+b=1.

According to the present invention, preferably, in step (1), the transition metal salt is selected from at least one of chloride, sulfate, carbonate, nitrate, phosphate and acetate of transition metal; The concentration of the transition metal salt is 0.01-10 mol/L.

According to the present invention, preferably, in step (1), the antioxidant is selected from at least one of ascorbic acid, erythorbic acid, hydrazine hydrate, ferrous sulfate, sodium sulfite and sodium borohydride; the concentration of the antioxidant is 0.01～5mol/L.

According to the present invention, preferably, in step (1), the complexing agent is selected from at least one of citric acid, maleic acid, lycium acid, ethylenediaminetetraacetic acid and ammonia; The molar amount is 1-20 times the molar amount of the transition metal salt.

According to the present invention, preferably, in step (2), the concentration of the sodium ferrocyanide is 0.01-10 mol/L.

According to the present invention, preferably, in step (1) and step (2), the pH adjusting agent is each independently selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, ammonia, sodium hydroxide, sodium carbonate, and sodium bicarbonate. One type, the pH of each solution is independently between 5.5 and 7.5 after adding a pH regulator.

According to the present invention, preferably, in step (1) and step (2), the sodium salt is each independently selected from sodium chloride, sodium sulfate, sodium nitrate, sodium acetate, trisodium citrate, ethylenediamine tetra At least one of disodium acetate and tetrasodium edetate; the amount of the sodium salt is 0.01-10 mol/L independently.

According to the present invention, preferably, in step (3), the mixed solution containing transition metal salt and the mixed solution containing sodium ferrocyanide are added dropwise by a metering pump, and the dropping rate is independently 1 to 500. Ml/min.

According to the present invention, preferably, in step (3), the stirring speed is 100 to 1200 revolutions per minute; the stirring time is 6 to 72 hours.

According to the present invention, preferably, in step (3), the standing time is 1 to 48 hours.

According to the present invention, preferably, in step (3), the spray drying temperature is independently between 60 and 200°C.

According to the present invention, preferably, in each step, the protective atmosphere is independently selected from at least one of argon, nitrogen, and hydrogen; and the certain temperature is independently between 0 and 80°C.

According to the present invention, preferably, in step (4), the temperature of the inert atmosphere heat treatment or vacuum drying is between 100°C and 400°C.

The second aspect of the present invention provides a Prussian blue sodium ion battery cathode material prepared by the above preparation method.

The third invention of the present invention provides a sodium ion battery, comprising a negative electrode material, a glass fiber separator, an organic electrolyte and a positive electrode material, the negative electrode material is metallic sodium and/or hard carbon material, and the positive electrode material is the aforementioned Prussian blue Cathode material for sodium ion battery. The sodium ion battery can be manufactured by assembling the above-mentioned parts in a conventional manner in the field, and the present invention is not particularly limited to this.

Compared with the Prussian blue sodium ion battery cathode material synthesized by the co-precipitation technology, the excellent effects of the present invention are as follows:

1. The Prussian blue cathode material synthesized in the present invention has low moisture content, stable material structure, and excellent electrochemical performance, mainly due to the slow crystallization of the material and the subsequent heat treatment process. The addition of the complexing agent makes the transition metal ion slowly react with ferrocyanide. In order to avoid the direct mixing of the transition metal salt solution and the sodium ferrocyanide solution, the reaction speed is too fast. It can effectively reduce the reaction concentration to slow down the reaction speed. In addition, the subsequent heat treatment process can further remove the moisture in the Prussian blue material, so that the material exhibits a higher specific capacity and excellent electrochemical performance.

2. The preparation method of the Prussian blue sodium ion battery cathode material with low moisture content provided by the present invention is simple and easy to operate. By adjusting the reactant concentration ratio, temperature, pH, speed and other parameters combined with the subsequent heat treatment process, the material exhibits excellent electrochemical performance, and it is easy to achieve expanded production and practical application.

Other features and advantages of the present invention will be described in detail in the following specific embodiments.

Description of the drawings

By describing the exemplary embodiments of the present invention in more detail with reference to the accompanying drawings, the above and other objectives, features, and advantages of the present invention will become more apparent.

FIG. 1 is a thermogravimetric curve diagram of the Prussian blue cathode material for sodium ion battery with water and low moisture content prepared in Example 5 of the present invention.

2 is a graph showing the first charge and discharge curve of the Prussian blue cathode material for low moisture content sodium ion battery prepared in Example 5 of the present invention at a current density of 10 mA/g.

3 is a performance diagram of the Prussian blue cathode material for low-moisture sodium ion battery prepared in Example 5 of the present invention under a current density of 100 mA/g for 200 charge-discharge cycles.

Detailed ways

The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

Example 1

This example is used to illustrate the preparation of the low-moisture content Prussian blue cathode material and sodium ion battery of the present invention.

1. Preparation of Prussian blue cathode material with low moisture content:

(1) Fill container A with nitrogen at 35° C., add 200 ml of deionized water, and then sequentially dissolve 0.2 g of ascorbic acid, 8 mmol of ferrous sulfate heptahydrate, 14 mmol of citric acid, and 8 mmol of sodium sulfate in container A. Fill container B with nitrogen at 35℃, add 200ml ionized water, and then sequentially dissolve 0.2g ascorbic acid, 6mmol sodium ferrocyanide decahydrate, 14mmol citric acid, 8mmol sodium sulfate in container B, and finally in the container respectively Ammonia water was added to A and B to adjust the pH=6.8.

(2) Fill container C with nitrogen at 35°C, and then add the solutions in containers A and B to container C simultaneously at a rate of 3ml/min through metering pumps. The stirring speed in container C is 800 rpm. /Hour, after all the solutions in containers A and B are added to container C, continue to stir for 8 hours.

(3) Then the solution is allowed to stand for 24 hours, and then the supernatant of the solution is removed, the remaining slurry is centrifuged and washed 3 times, and then spray-dried at 150°C, the molecular formula is Na _1.82 FeFe(CN) ₆ ·1.8H ₂ O Prussian blue cathode material.

(4) The _{_{Na 1.82 FeFe (CN) 6 ·}} 1.8H 2 O Prussian blue cathode material dried for 8 hours under nitrogen for 200 ℃, i.e., to obtain a low moisture content of _{_{Na 1.82 FeFe (CN) 6 ·}} 0.9H 2 O Prussia Blue cathode material.

2. Preparation of sodium ion battery:

The obtained Prussian blue cathode material with low moisture content is made into an electrode sheet, which is assembled with a glass fiber separator, metallic sodium, and organic electrolyte to obtain a sodium ion battery.

Example 2

1. Preparation of Prussian blue cathode material with low moisture content:

(1) Fill container A with nitrogen at 30° C., add 200 ml of deionized water, and then sequentially dissolve 0.2 g of ascorbic acid, 8 mmol of ferrous sulfate heptahydrate, 10 mmol of citric acid, and 6 mmol of sodium sulfate in container A. Fill container B with nitrogen at 30℃, add 100ml ionized water, and then successively dissolve 0.2g ascorbic acid, 6mmol sodium ferrocyanide decahydrate, 10mmol citric acid, 6mmol sodium sulfate in container B, and finally in the container respectively Ammonia water was added to A and B to adjust the pH=6.8.

(2) Blow nitrogen into vessel C at 30°C, and then add the solutions in vessel A and B to vessel C simultaneously at a rate of 3ml/min through metering pumps. The stirring speed in vessel C is 900 rpm. /Hour, after all the solutions in containers A and B are added to container C, continue to stir for 12 hours.

(3) The solution was then allowed to stand for 24 hours, and then the supernatant of the solution was removed, and the remaining slurry was centrifuged and washed 3 times with water, followed by spray drying at 160°C. That is, the Prussian blue cathode material with the molecular formula Na _1.89 FeFe(CN) ₆ ·1.6H _{2 O is obtained.}

(4) _{Dry the Prussian blue cathode material with Na 1.89} FeFe(CN) ₆ ·1.6H ₂ O at 250°C for 12 hours to obtain Prussian blue with low moisture content Na _1.82 FeFe(CN) ₆ ·0.5H ₂ O Cathode material.

2. Preparation of sodium ion battery:

The obtained Prussian blue cathode material is made into an electrode sheet, which is assembled with a glass fiber separator, metallic sodium, and organic electrolyte to obtain a sodium ion battery.

Example 3

1. Preparation of Prussian blue cathode material with low moisture content:

(1) Fill container A with argon at 25° C., add 300 ml of deionized water, and then sequentially dissolve 0.3 g of ascorbic acid, 8 mmol of ferrous sulfate heptahydrate, 14 mmol of citric acid, and 8 mmol of sodium sulfate in container A. Fill container B with argon at 25°C, add 300ml of ionized water, and then successively dissolve 0.3g ascorbic acid, 6mmol sodium ferrocyanide decahydrate, 14mmol citric acid, 8mmol sodium sulfate in container B, and finally Ammonia water was added to the containers A and B to adjust the pH=6.6.

(2) Fill container C with argon gas at 25°C, and then add the solutions in containers A and B to container C simultaneously at a rate of 4ml/min through metering pumps. The stirring speed in container C is 1000 Revolution per hour, after all the solutions in containers A and B are added to container C, continue to stir for 8 hours.

(3) The solution was then allowed to stand for 24 hours, and then the supernatant of the solution was removed, and the remaining slurry was centrifuged and washed 3 times with water, followed by spray drying at 140°C. That is, the Prussian blue cathode material with the molecular formula Na _1.91 FeFe(CN) ₆ ·1.4H _{2 O is obtained.}

(4) _{Dry the Prussian blue cathode material with Na 1.91} FeFe(CN) ₆ ·1.6H ₂ O at 280°C for 12 hours to obtain Prussian blue with low moisture content Na _1.82 FeFe(CN) ₆ ·0.3H ₂ O Cathode material.

2. Preparation of sodium ion battery:

Example 4

1. Preparation of Prussian blue cathode material with low moisture content:

(1) Blow nitrogen into vessel A at 20°C, add 200ml of deionized water, and then dissolve 0.25g of ascorbic acid, 5mmol of ferrous sulfate heptahydrate, 10mmol of citric acid, and 10mmol of sodium sulfate in vessel A in sequence. Fill container B with nitrogen at 20°C, add 200ml of ionized water, and then successively dissolve 0.25g ascorbic acid, 6mmol sodium ferrocyanide decahydrate, 10mmol citric acid, and 14mmol sodium sulfate in container B, and finally in the container respectively Ammonia water was added to A and B to adjust the pH=6.7.

(2) Blow nitrogen into vessel C at 25°C, and then add the solutions in vessels A and B to vessel C simultaneously at a rate of 6ml/min through metering pumps. The stirring speed in vessel C is 800 rpm. /Hour, after all the solutions in containers A and B are added to container C, continue to stir for 14 hours.

(3) The solution was then allowed to stand for 8 hours, and then the supernatant of the solution was removed, and the remaining slurry was centrifuged and washed 3 times with water, followed by spray drying at 140°C. That is, the Prussian blue cathode material with the molecular formula Na _1.94 FeFe(CN) ₆ ·0.8H _{2 O is obtained.}

(4) _{The Prussian blue cathode material of Na 1.94} FeFe(CN) ₆ ·0.8H ₂ O was dried under nitrogen at 260° C. for 10 hours to obtain the Prussian blue cathode material _{of Na 1.94} FeFe(CN) _{6 with low moisture content.}

2. Preparation of sodium ion battery:

Example 5

1. Preparation of Prussian blue cathode material with low moisture content:

(1) Fill container A with nitrogen at 50° C., add 100 ml of deionized water, and then sequentially dissolve 0.05 g of ascorbic acid, 7 mmol of ferrous sulfate heptahydrate, 11 mmol of citric acid, and 12 mmol of sodium sulfate in container A. Fill container B with nitrogen at 50°C, add 100ml of ionized water, and then sequentially dissolve 0.05g ascorbic acid, 5mmol sodium ferrocyanide decahydrate, 14mmol citric acid, 8mmol sodium sulfate in container B, and finally in the container respectively Ammonia water was added to A and B to adjust the pH=6.5.

(2) Fill container C with nitrogen at 50°C, and then add the solutions in containers A and B to container C simultaneously at a rate of 6ml/min through metering pumps. The stirring speed in container C is 1200 rpm. /Hour, after all the solutions in containers A and B are added to container C, continue to stir for 10 hours.

(3) Then the solution is allowed to stand for 24 hours, and then the supernatant of the solution is removed, and the remaining slurry is centrifuged and washed 3 times with water, followed by spray drying at 120°C, and vacuum drying at 180°C for 12 hours. That is, the Prussian blue cathode material with the molecular formula Na _1.87 FeFe(CN) ₆ ·1.9H _{2 O is obtained.}

(4) _{The Prussian blue cathode material of Na 1.87} FeFe(CN) ₆ ·1.9H ₂ O was dried in argon gas at 260° C. for 10 hours to obtain the Prussian blue cathode material _{of Na 1.87} FeFe(CN) _{6 with low moisture content.}

2. Preparation of sodium ion battery:

Test case 1

Thermogravimetric experiments and charge-discharge experiments were performed on the Prussian blue cathode material for sodium ion battery and sodium ion battery prepared in Example 5 of the present invention with water and low moisture content. The results are shown in Figures 1 to 3, in which Figure 1 is a thermogravimetric curve diagram of the Prussian blue cathode material for sodium ion batteries with water and low moisture content prepared in Example 5 of the present invention. 2 is a graph showing the first charge and discharge curve of the Prussian blue cathode material for low moisture content sodium ion battery prepared in Example 5 of the present invention at a current density of 10 mA/g. 3 is a performance diagram of the Prussian blue cathode material for low-moisture sodium ion battery prepared in Example 5 of the present invention under a current of 100 mA/g for 200 charge-discharge cycles.

It can be seen from Figures 1 to 3 that the moisture of the Prussian blue cathode material dried by argon at 260°C has been completely removed, the first discharge specific capacity is 139mAh/g, and the capacity retention rate after 200 cycles is 100%, which shows that the present invention The low moisture content of Prussian blue cathode material has excellent electrochemical performance.

Test case 2

The Prussian blue cathode materials prepared in the above examples were subjected to thermogravimetric test respectively, and then the first charge-discharge test was performed at a current density of 10mA/g, and then a 200-cycle performance test was performed at a current density of 100mA/g. The measured data are shown in the table 1 shows:

Table 1

It can be seen from Table 1 that the Prussian blue cathode material of the present invention has low moisture content, high first discharge specific capacity and cycle capacity retention rate.

The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and spirit of the illustrated embodiments, many modifications and changes are obvious to those of ordinary skill in the art.

Claims

A preparation method of a Prussian blue sodium ion battery cathode material with low moisture content, characterized in that the preparation method comprises the following steps:

(1) Dissolve transition metal salts, antioxidants, complexing agents, pH regulators, and sodium salts in water under an inert atmosphere and a certain temperature to obtain a mixed solution containing transition metal salts;

(2) Dissolve sodium ferrocyanide, pH adjuster, and sodium salt in water under an inert atmosphere and a certain temperature to obtain a mixed solution containing sodium ferrocyanide;

(3) Add dropwise the mixed solution containing transition metal salt and the mixed solution containing sodium ferrocyanide into a container with an inert atmosphere and a certain temperature, and then stir, stand still, and then wash, filter or centrifuge , Spray drying to obtain powdered Prussian blue sodium ion battery cathode material;

(4) The powdered Prussian blue sodium ion battery cathode material is subjected to inert atmosphere heat treatment or vacuum drying to obtain a Prussian blue sodium ion battery cathode material with low moisture content.
The method for preparing a cathode material for Prussian blue sodium ion battery with low moisture content according to claim 1, wherein the molecular formula of the cathode material for Prussian blue sodium ion battery with low moisture content is Na x M a N b Fe(CN) 6 ·YH 2 O, where 1.8<x<2, 0≤y≤3; M and N are transition metals, each independently selected from Fe, Co, Mn, Ni, Cu, Zn, Cr, V, Zr and Ti At least one of, where 0<a<1, 0<b<1, a+b=1.
The method for preparing a Prussian blue sodium ion battery cathode material with low moisture content according to claim 1, wherein, in step (1),

The transition metal salt is selected from at least one of transition metal chloride, sulfate, carbonate, nitrate, phosphate and acetate; the concentration of the transition metal salt is 0.01-10 mol/L;

The antioxidant is selected from at least one of ascorbic acid, erythorbic acid, hydrazine hydrate, ferrous sulfate, sodium sulfite, and sodium borohydride; the concentration of the antioxidant is 0.01-5 mol/L;

The complexing agent is selected from at least one of citric acid, maleic acid, lycic acid, ethylenediaminetetraacetic acid and ammonia; the molar amount of the complexing agent is 1 to 1 of the molar amount of the transition metal salt. 20 times.
The method for preparing a Prussian blue sodium ion battery cathode material with low moisture content according to claim 1, wherein in step (2), the concentration of the sodium ferrocyanide is 0.01-10 mol/L.
The method for preparing a Prussian blue sodium ion battery cathode material with low moisture content according to claim 1, wherein, in step (1) and step (2),

The pH adjusters are each independently selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, ammonia, sodium hydroxide, sodium carbonate, and sodium bicarbonate. After the pH adjuster is added, the pH of each solution is independently between 5.5 and 7.5. between;

The sodium salt is each independently selected from at least one of sodium chloride, sodium sulfate, sodium nitrate, sodium acetate, trisodium citrate, disodium edetate, and tetrasodium edetate; The amount of sodium salt used is 0.01-10 mol/L each independently.
The method for preparing a low-moisture content Prussian blue sodium ion battery cathode material according to claim 1, wherein, in step (3),

Using a metering pump to drop the mixed solution containing transition metal salt and the mixed solution containing sodium ferrocyanide, the dropping rate is independently 1 to 500 ml/min;

The stirring speed is 100 to 1200 revolutions per minute; the stirring time is 6 to 72 hours; the standing time is 1 to 48 hours;

The temperature of the spray drying is each independently between 60°C and 200°C.
The method for preparing a Prussian blue sodium ion battery cathode material with low moisture content according to claim 1, wherein in each step, the inert atmosphere is independently selected from at least one of argon, nitrogen, and hydrogen; The certain temperature is independently between 0 and 80°C.
The method for preparing a low-moisture content Prussian blue sodium ion battery cathode material according to claim 1, wherein, in step (4), the temperature of the inert atmosphere heat treatment or vacuum drying is between 100 and 400°C.
A Prussian blue sodium ion battery cathode material prepared by the preparation method of any one of claims 1-8.
A sodium ion battery, comprising a negative electrode material, a glass fiber separator, an organic electrolyte and a positive electrode material, wherein the negative electrode material is metallic sodium and/or hard carbon material, and the positive electrode material is described in claim 9 Prussian blue sodium ion battery cathode material.